chore: update license year and refine error message for HTTP client requirement

Author: reeshika-h

LICENSE

@@ -1,6 +1,6 @@
 MIT License
 
-Copyright (c) 2012-2025 Contentstack
+Copyright (c) 2012-2026 Contentstack
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

lib/core/errorMessages.js

@@ -21,7 +21,7 @@ export const ERROR_MESSAGES = {
   NO_APP_AUTHORIZATIONS: 'No authorizations found for the app. Verify app configuration and try again.',
 
   // Concurrency queue errors
-  AXIOS_INSTANCE_MISSING: 'Axios instance is not present. Initialize the HTTP client and try again.',
+  AXIOS_INSTANCE_MISSING: 'HTTP client is required. Initialize the HTTP client and try again.',
   MIN_CONCURRENT_REQUESTS: 'Concurrency Manager Error: Minimum concurrent requests must be at least 1.',
   MIN_RETRY_LIMIT: 'Retry Policy Error: Minimum retry limit must be at least 1.',
   MIN_RETRY_DELAY: 'Retry Policy Error: Minimum retry delay must be at least 300ms.',

test/unit/concurrency-Queue-test.js

@@ -189,7 +189,7 @@ describe('Concurrency queue test', () => {
       new ConcurrencyQueue({ axios: undefined })
       expect.fail('Undefined axios should fail')
     } catch (error) {
-      expect(error.message).to.be.equal('Axios instance is not present. Initialize the HTTP client and try again.')
+      expect(error.message).to.be.equal('HTTP client is required. Initialize the HTTP client and try again.')
       done()
     }
   })